Spectrophotometric study of the complexation equilibria of zirconium(IV) with 1-amino-4-hydroxyanthraquinone and the determination of zirconium

Abstract

The spectral absorption and acid-base characteristics of 1-amino-4-hydroxyanthraquinone (AMHA) were studied in water-ethanol media. The composition, molar absorptivities, equilibrium constants and stability constants of the chelates of this reagent with zirconium(IV) have been determined spectrophotometrically in 40%V/V ethanol at 20 °C and an ionic strength of 0.1 M(NaClO₄). Graphical logarithmic analysis of the absorbance graphs was used to demonstrate and characterise the complexation equilibria in solution. A simple, rapid, selective and sensitive method for the spectrophotometric determination of trace amounts of zirconium is proposed based on the formation of the Zr(AMHA)₂ complex at pH 3.5 (λ_max.= 600 nm, ε= 1.621 × 10⁴ l mol^–1 cm^–1). Interference caused by a number of ions was masked by the addition of cyanide ions.